The long-term goal of this project is elucidation of the multi-cellular mechanisms of neural processing the auditory and vestibular systems. The immediate goal is development of a novel technique for simultaneously recording activity from many axons in a nerve. Regeneration-type neural interface devices will be used in an attempt to record action potentials simultaneously from several microelectrodes distributed throughout the cross-section of the anuran eighth nerve. The basic approach taken is to interpose a silicon substrate that is perforated by a number of via holes between the surgically severed ends of a nerve capable of regeneration. Regenerating axons grow through the via holes, and thus become spatially fixed with respect to microelectrodes on the substrate. The microelectrodes allow the neural signals to be recorded using external circuitry, providing a direct interface to neural signal pathways. Should this approach prove to be feasible, it will offer an unprecedented opportunity to study multi-cellular neural processing, not only in the anuran inner ear, but in any nerve capable of regeneration. This project will consist of five tasks: (1) an electrophysiological and histological evaluation of the anuran eighth nerve's regeneration response to the implantation of neural interface devices, (2) fabrication of neural interface devices optimized for implantation in this nerve, (3) development of the requisite hardware and software to permit simultaneous, computer-controlled acquisition and processing of multiple signals from the neural interfaces, (4) in vivo measurement of the recording selectivity of various microelectrode site designs, and (5) preliminary studies to determine if multiaxon phase-locking is employed in coding acoustic stimuli in the eighth nerve. Completion of these feasibility studies will make possible a future project phase, in which the major focus would be the application of this multi-axon recording technique in more detailed studies of hearing biophysics and neural signal processing.